The present invention relates to conveyors, and particularly to radial stackers which may be lowered and transported on highways, using their own wheels.
A radial stacker is a conveyor having a raised discharge end and an infeed end which is pivotally located at a central location. The stacker is movable about the central location to form an arcuate stack of material such as gravel and the like.
The desirability of providing a radial stacker which is easily transportable by highway has been clearly recognized in recent years. There are, however, several factors which make highway transportation of such conveyors somewhat difficult.
Because of their length and height radial stackers require a wide base resting on the ground to provide stability during operation. In the operating configuration, the lower or infeed end of the conveyor is pivotably located at a relatively fixed position, and the upper or discharge end of the conveyor is movably supported by wheels. These wheels are preferably spaced widely apart from the central longitudinal axis of the conveyor, to provide stability as well as support for the upraised conveyor. This width, however, often exceeds the maximum allowable width for highway operation of a vehicle.
The amount of material which can be stacked by a radial stacker is limited by the height of the upper or discharge end of the stacker, and by the distance to which the conveyor extends beyond the position of the wheels. It is therefore desirable to have a very long conveyor. This length, however, also often exceeds the maximum permissible length for highway transportability.
Various ways are known for reducing the overall width of radial stackers to provide for legal highway transport. For example, Penterman, et al., U.S. Pat. No. 4,135,614 discloses a portable radial stacker including a mechanism for swinging short outer end portions of its transverse axle assembly between an extended radial stacker operating configuration and a highway transport configuration. The axle assembly disclosed by Penterman et al., however, provides an unnecessarily limited width for the stacker in its operational configuration, as well as unnecessarily great overall width in the transport configuration.
Rath U.S. Pat. No. 3,552,546 discloses a radial stacker in which the main transverse axle member extends and contracts telescopically to change the width of the supporting structure between a wide operational width and a narrower highway transport width. This construction, however, is unnecessarily complex and expensive. A simpler, less expensive means for providing adjustable width is desired.
Other arrangements are known for realigning wheels from a transport configuration to a radial stacking configuration, as exemplified in Barber U.S. Pat. No. 17,160. However, arrangements of these types do not provide any additional width in the radial stacker configuration, and therefore do not provide the desired stability of the stacker during operation.
Another consideration in a transportable radial stacker is that the apparatus should remain stable during conversion from its operating to its transport configuration. This does not appear to have been directly addressed in previously known radial stackers.
Numerous arrangements are known for utilizing hydraulic piston and cylinder assemblies, or other motors, to reduce the length of an extremely long conveyor by folding portions of the conveyor reversely along other portions of the conveyor. Examples of such hydraulically powered conveyor folding arrangements are shown in Moy U.S. Pat. No. 3,051,295, Spellman, Jr., U.S. Pat. No. 3,493,136, Rossi U.S. Pat. No. 3,599,784, and Penterman et al. U.S. Pat. No. 4,135,614. In all of these mechanisms, however, the piston shaft of a hydraulic ram is exposed when the conveyor is in its operational configuration. As a result, the piston shaft is susceptible to being damaged when such a coveyor is used for handling abrasive materials such as sand and gravel.
The hydraulic motors used for folding conveyors are ordinarily employed in parts, with one hydraulic motor on each side of the conveyor, as disclosed by Penterman et al. Any imbalance between the forces provided by the hydraulic motors of a pair may cause undesirable wracking and twisting forces which could jam the folding mechanism involved. Additionally, the hydraulic motors and linkages connecting segments of such conveyors are often unprotected during use of the conveyors.
What is desired, therefore, is an improved transportable radial stacker apparatus whose structure is variable between a shortened narrow configuration which is legal for highway transport and an operating configuration providing an increased separation between the wheels supporting the conveyor in its raised position. Also desired is a mechanism for folding such a radial stacker to a reduced overall length which permits legal highway transport of the apparatus and in which the folding mechanism is protected when the stacker is in its operating configuration.